Motor-generators, such as a belt-driven integrated starter generator (ISG), may be used in assisting the operation of an engine by providing additional torque, or by supplying electrical power to an electrical system of a vehicle. Belt tension of an accessory drive pulley of an ISG is typically monitored in order to reduce friction losses.
Belt tension may be monitored by way of a passive tension system, for example. Alternatively, belt tension may be monitored by actively controlled tensioner devices to increase belt tension only when high torque demands are made.
However, the inventors herein have recognized potential issues with such systems. Passive tensioning systems are set at a tension sufficient to avoid slip at a maximum operating torque, which may result in a reduction of fuel efficiency. Actively controlled tensioner devices may be less reliable and require electronic actuators which may be more costly. Furthermore, spring-biased tensioning devices require additional knowledge of a spring rate and may be prone to the effect of tolerances.
One potential approach to at least partially address some of the above issues includes a system and a method for a belt slip monitor wherein belt tension and belt slippage may be monitored, and belt tension and/or operational torque may be adjusted based on monitoring belt slippage.
In one example, a belt slip monitor for a belt coupled to a motor-generator, may comprise a first movable portion movable with respect to the motor-generator, a second movable portion movably coupled to the first movable portion, the second movable portion being coupled to the belt such that operational states of the first and second movable portions of the belt slip monitor are dependent upon the tension in the belt, a first sensor configured to determine the operational state of the first movable portion, and a second sensor configured to determine the operational state of the second movable portion, wherein the belt slip monitor is configured to determine whether the belt is slipping based on the operational state of the first and second movable portions.
In this way, the belt slip monitor, a passive tensioning device, may detect slip both when the ISG transmits torque to the system, and removes torque from the system. Further, the belt slip monitor system may adjust operational torque, and thereby belt tension, so that fuel efficiency may increase, unlike known passive tensioner devices that must operate at a high tension.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.